Immunotoxicology of Halogenated Aromatic Hydrocarbons

Halogenated aromatic hydrocarbons (HAHs) persist in the environment and pose a threat to human health. The immune system is a sensitive target of HAHs. Over the past several decades, research in animal models and in human populations supports that HAHs are immunotoxic. The effects of some HAHs have been studied very broadly, whereas other effects have been interrogated in detail. The complex nature of the immune system involves many different cell types, such as T cells, dendritic cells, macrophages, natural killer cells, and neutrophils, which originate from hematopoietic stem cells and lineage-specific precursors. HAH immunotoxicity to cells of the primary immune organs, and to specific adaptive and innate immune cells, has been reported. Given that HAH immunotoxicity has been known for about 40 years, the main focus of this article is to summarize the recent findings and to discuss how this emerging information suggests possible cellular and molecular mechanisms of HAH immunotoxicity. The article will also present an overview of emerging data that point to HAH-mediated changes in innate immunity, immunological memory, as well as new information regarding HAH developmental immunotoxicity.